Adult-Onset Nesidioblastosis: A Challenging Diagnosis Revealed by Endoscopic Ultrasonography.

BACKGROUND Nesidioblastosis is one of the possible causes of endogenous hyperinsulinemic hypoglycemia. This diagnosis usually occurs in infants, but in rare cases it can affect adult patients. Due to its rarity, diagnostic confirmation can be challenging and clinically overlap with other diagnoses associated with hypoglycemic symptoms, often requiring management at a specialized center. CASE REPORT In this article, we present the case of a 27-year-old female patient who had experienced clinical symptoms of hypoglycemia of unknown origin for several years. Macroscopically, no focal pancreatic lesions were identified on computed tomography, magnetic resonance imaging, or ⁶⁸Gallium DOTA-D-Phe1-Tyr3-Octreotide imaging. However, endoscopic ultrasonography revealed nonspecific heterogeneous pancreatic tissue measuring 8.2×6.8 mm in the body and tail of the pancreas. Subsequent histopathologic examination of a small tissue sample demonstrated an increased number of b cells with enlarged hyperchromatic nuclei or prominent nucleoli. The exocrine portion of the pancreas was preserved. This case report highlights the diagnostic challenges associated with identifying nesidioblastosis in an adult patient and outlines our diagnostic approach, therapeutic strategy, and clinical outcomes. CONCLUSIONS Nesidioblastosis should be considered a potential cause of hyperinsulinemic hypoglycemia in adult patients who exhibit persistent hypoglycemic symptoms without macroscopic correlates on imaging methods. Endoscopic ultrasonography may serve as a valuable modality for enhancing visualization of pancreatic tissue heterogeneity, particularly when no unequivocal lesion is detectable on other imaging techniques. Based on our experience, distal pancreatectomy alone appears sufficiently effective in eliminating hypoglycemic symptoms without inducing exocrine or endocrine pancreatic insufficiency.